1. The Field of the Invention
The present invention relates to metal ceramic composites, particularly beryllium metal matrix composites having dispersed beryllium oxide particles. Novel processes for fabricating metal ceramic composites are also described. The resulting composites are useful as cores, enclosures, packages and component parts for electronic board applications.
2. State of the Art
Conventional electronic packages typically include an integrated circuit device housed in a cavity formed by structural components which provide physical and electronic insulation from the environment. To accomplish the insulation function, packaging components must exhibit certain physical properties expressed in terms of high modulus of elasticity (hereinafter also `modulus`) and good fracture strength; good dielectric properties; high thermal conductivity (K); low coefficient of thermal expansion (CTE) and capacity for high density devices. Packaging materials must have surface characteristics which permit brazing or soldering to form a hermetic seal. Light weight and high stiffness are also preferred.
Several known materials have been used for electronic packaging, including 6061-type aluminum, molybdenum and KOVAR, an iron-based metal alloyed with cobalt and nickel. These prior art materials exhibit some, but not all, of the preferred characteristics. Accordingly, the selection of packaging materials typically involved a "trade off" between different physical and thermal properties. In view of the present invention, it is not necessary to compromise one property in favor of another.
Modern packaging materials are now expected to meet high reliability specifications for military and aerospace applications. New manufacturing technologies place additional demands on the physical and thermal requirements of packaging and substrate materials. One manufacturing technique, conventionally known as surface mount technology (SMT), involves the direct application of electronic components to an electric board. For this technique the electronic board must have the necessary mechanical properties to withstand fabrication of the electronic component directly on the board. The board must also maintain its physical integrity to perform the housing and insulation functions.
This direct application technique also requires compatible coefficients of thermal expansion for the electronic component and board. Otherwise, mechanical forces created by differential expansion or contraction during manufacture or subsequent operation may result in a failure of the component-board bond. Under extreme circumstances these mechanical forces may be sufficient to destroy the component parts or board.